<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <div onclick="console.log('first div')">
           <div onclick="console.log('second div')">
            <button onclick="console.log('button')"> Click</button>
        </div>
    </div>
    <script>
    //单击按钮时event,target是什么 button
    // 事件委托后添加的有效
    // 导致事件的最深元素的嵌套是事件的目标
    // 可以通过event.stopPropagation阻止事件的冒泡
    </script>
</body>
</html>